refactor!: Coins Add and Sub Consistency

[alexanderbez]

Description

Closes: #11687

Make Coins#Sub and Coins#SafeSub consistent with Coins#Add.

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[codecov]

Codecov Report

Merging #11689 (8fa296b) into master (610b2ee) will increase coverage by 0.02%.
The diff coverage is 96.66%.

@@            Coverage Diff             @@
##           master   #11689      +/-   ##
==========================================
+ Coverage   65.84%   65.86%   +0.02%     
==========================================
  Files         667      667              
  Lines       70446    70446              
==========================================
+ Hits        46387    46402      +15     
+ Misses      21365    21349      -16     
- Partials     2694     2695       +1     

Impacted Files	Coverage Δ
x/simulation/util.go	0.00% <0.00%> (ø)
types/coin.go	93.11% <100.00%> (-0.46%)	⬇️
x/auth/client/testutil/suite.go	97.53% <100.00%> (ø)
x/auth/vesting/types/vesting_account.go	87.18% <100.00%> (ø)
x/authz/simulation/operations.go	66.97% <100.00%> (ø)
x/bank/keeper/send.go	83.07% <100.00%> (ø)
x/bank/keeper/view.go	83.33% <100.00%> (ø)
x/bank/simulation/operations.go	81.02% <100.00%> (ø)
x/bank/types/send_authorization.go	55.55% <100.00%> (ø)
x/distribution/simulation/operations.go	90.27% <100.00%> (+9.72%)	⬆️
... and 8 more

[fedekunze]

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